When a vulnerable road user, such as a pedestrian or a cyclist, is hit by a front of a vehicle, e.g., when crossing a street, there is a risk that the vulnerable road user is thrown into the air and lands on the vehicle, e.g., on the bonnet or the windscreen. In particular, there is a risk that a head of the vulnerable road user impacts with the vehicle. In order to mitigate the consequences of such an impact, it is known technology to raise the bonnet, e.g., by means of an airbag and/or a pyrotechnic means, in order to create a gap between the bonnet and any hard parts below the bonnet, which could pose a potential risk for injury to the vulnerable road user.
An example of such a hard part located below the bonnet is the hinge arrangement for the bonnet. The hinge arrangement is used to open the bonnet by rotation around a first pivot axis located in the hinge arrangement, e.g., in order to gain access to an engine compartment for maintenance or repair. There may be a hinge arrangement adjacent to each lateral side of the rear end of the bonnet, i.e., the end located towards the windscreen. If the vulnerable road user impacts with the bonnet in a region above the hinge arrangement, there is a risk that the head will impact with the hinge arrangement via the bonnet, when the bonnet deforms downwards because of the impact. Often, the part of the hinge arrangement comprising the pivot axis is located directly, or very closely, below the bonnet and thus poses a potential injury risk for a head impacting with the bonnet above this position.
In order to reduce such risks, it is known technology to locate the hinge arrangement close to the lateral side of the vehicle. However, such a location will restrict the possible configuration and design of the bonnet, the A-pillar, the front fender and/or the hinge arrangement.
The Head Injury Criterion, herein abbreviated as HIC, is a measure of the likelihood of a head injury arising from an impact. The HIC value can be used to assess safety related to vehicles. It is defined as:
  HIC  =                    max        ⁡                  [                                    1                                                t                  2                                -                                  t                  1                                                      ⁢                                          ∫                                  t                  1                                                  t                  2                                            ⁢                                                a                  ⁡                                      (                    t                    )                                                  ⁢                                                                  ⁢                                  ⅆ                  t                                                              ]                    25        ⁢          (                        t          2                -                  t          1                    )      
wherein t1 and t2 are two arbitrary times during the acceleration pulse. Acceleration is measured in multiples of the acceleration of gravity, g, and time is measured in seconds. For the values mentioned herein, HIC is evaluated over a maximum 15 milliseconds time interval. The calculation of HIC is further described in the document “Development of Improved Injury Criteria for the Assessment of Advanced Automotive Restraint Systems—II”, by Eppinger et al, published in November 1999.
In order to reduce the likelihood of a head injury, the HIC value should be low. It is desirable that the HIC value should be below 1750, preferably below 1500, more preferably below 1000 and most preferably below 650. Some countries have legal requirements for the HIC value. See for example Global Technical Regulation No. 9 Pedestrian Safety, Directive 2003/102/EC or TRIAS 63, Japan.
When evaluating the likelihood of a head injury for a pedestrian being hit by a vehicle and landing on the bonnet, HIC values are determined for a grid of points on a surface of the bonnet. This surface is at least partly delimited by a line representing a 45 degree tangent, i.e. the surface is mainly on the relatively flat portion of the bonnet, leaving the curved portions, e.g. the front fenders, outside this surface. See e.g., the EuroNCAP test described in “European New Car Assessment Programme, Pedestrian Testing Protocol”, Version 6.2.1, February 2013.
In the above-mentioned example of known technology, i.e., locating the hinge arrangement close to the lateral side of the vehicle, the hinge arrangement will be outside the grid used for the HIC measurement. Thus the HIC measurement will in that case not be influenced by the hinge arrangement. However, the risk of head injury caused by the hinge arrangement is still there, if the vulnerable road user would land in a region above the hinge arrangement, e.g., at an oblique angle on the vehicle.